Effect of Ultrasound on Transdermal Permeation of Diclofenac

Abstract

During the last two decades the effects of ultrasound on the transdermal permeability to a wide variety of drugs have been extensively investigated. There is still some uncertainty regarding the mechanisms involved in ultrasonic permeation enhancement, thus we investigated the effect of ultrasonic treatment on the transdermal permeation of the NSAID, diclofenac. Experiments were conducted over two phases, consisting of different time periods, using a continuous flow-through diffusion system. It is clear from the present study that ultrasound enhanced the permeability of human skin to diclofenac released from a commercially available gel. These results were in contrast to those obtained for ibuprofen in an in vitro study across human skin, but in agreement with those obtained in two in vivo studies of the latter NSAID. Steady state flux values of diclofenac remained approximately 1.26 times higher than those of controls during the 24 h of the experiment. These observations concurred with those made in two previous in vivo studies. It was concluded that the enhancement of diclofenac permeation by sonication could not be adequately explained primarily on a thermal basis. Furthermore, the in vitro flow-through diffusion model was shown to have predictive value as an in vivo method for sonophoresis.